JP7177252B2 - Improved flexible dust boot for automotive brake cylinders - Google Patents

Description

The present invention relates to a resilient boot seal system for wheel brake actuation cylinders of motor vehicles. Such wheel brake cylinders are generally fixed by a stator attached to, for example, an axle, an anchor plate, etc., and are provided with relatively movable actuating members, such as brake shoes, for initiating the spreading movement between the brake pads. , may be embodied as electrical or mechanical actuators. More specifically and in addition to disc brakes, conventional drum brakes for vehicles are well known, often responsible for expanding hydraulic wheel brake cylinders having housings, hydraulic chambers and brake shoes. The actuating members generally comprise two hydraulically actuated radially actuating pistons . Each piston functions in the form of a displaceable wall that limits the volumetric capacity of hydraulic fluid within the pressure chamber of the housing. In this regard, the hydraulic The piston spreads between the two brake shoes under hydraulic pressure. A parking brake function mode can operate on the same cylinder with additional self-locking means. As a result, the brake shoes are urged into frictional contact with the sliding surface of the rotating brake drum. The pretension return spring serves to return/retain the brake shoe containing the piston when the drum brake is released.

Regardless of the particular brake type or cylinder type (electrical, hydraulic, mechanical), any relative displacement between the housing and the actuating member requires a gap between them, which keeps foreign objects out. What is needed is a sealing system comprising a flexible boot with a peripherally associated interface with a bellows disposed between the interfaces to flexibly avoid. A common problem with these cylinders is their cheap durability with improved corrosion resistance. That task is not easy to accomplish as wheel cylinders are mostly located in the relatively basic (low level) niche industry, which means that the cylinders are located in areas where they are exposed to weather and dirt. means Good protection against contamination by foreign matter such as dirt, liquids, gravel or mixtures thereof is important. Conventional dust boots are examples for the usual components of conventional wheel cylinders on hydraulic drum brakes, electric parking brakes and compound brakes. Such boots play a role in preventing dust from entering the inside of the wheel cylinder. This prevents damage to the seals or guidance between the working members (mainly hydraulic seal pistons) and the cylinder. A defective boot can create a risk of hydraulic brake fluid contamination or brake fluid leaking out and becoming contaminated. High-pressure spray cleaning systems can pose significant hazards due to the possibility of intrusion of cleaning fluids. While most known closed cylinder seal systems adequately meet the primary sealing requirements, at least as far as protection against foreign material intrusion is concerned, some new test results suggest that the It presents potential drawbacks, especially in service brake applications, including failure under high temperature service with respect to air or gas that may be present. Temperatures inside drum brake wheel cylinders can rise above 120° C. when exposed to exhaustive braking operation and/or extreme environmental conditions and/or limited cooling. With conventional closed boots, such temperature increases can lead to increased internal room pressures formed between the boot, the actuating member (piston) and the housing. As the temperature (pressure) inside the room rises, the conventional boot expands like a balloon due to thermal expansion. Such additional stresses may promote the boot interfaces to flip out of their seats or alternatively cause catastrophic failure through elastomeric boot rupture. Both faults result in a faulty seal function.

In improving sealability, US Pat. No. 5,200,000 discloses a boot comprising two interface sections each mounted circumferentially from the radially outer side (centered on the radially outer side), one of the interface sections being perforated. A drum brake cable actuation interface member having a seal system with an apparatus is disclosed. The flexible boot has bellows between interface sections to allow relative displacement between the actuating member and the housing. The brake cable linkage can be introduced from the back side of the housing. The interface section integrates small through-hole orifices that provide constant pressure equalization between the inside and outside of the boot. As a result, such a closed open boot design avoids uncontrolled flipping motion. For this reason, additional auxiliary shielding walls have been proposed arranged at the radially outer housing interface portion of the boot for additional protection against ingress of rainwater or spray water, for example cleaning fluids.

US Pat. No. 6,200,000 discloses an improvement in heat resistance and also robust mounting for a drum brake wheel cylinder, together with a housing having a cylinder bore provided therein, in which the piston is operable. and forming a fluid pressure chamber therewith, one end of the housing adjacent the cylinder being formed therein with a length and diameter greater than the cylinder bore, thereby providing a cylindrical recess with a protective shoulder. wherein the annular inner surface of said recess has a predetermined controlled micro-finish of roughness greater than said cylinder bore, and a link pin engages said piston and engages said cylinder for actuation of a brake shoe. by which the annular wheel cylinder boot is integrated into the housing. The packaging, especially the length of the assembly, can be improved, and the test program passes the weakness in protection against contamination, in particular the ingress of fluids such as rainwater, pressurized spray wash water, or the salt spray corrosion test. reveals weaknesses in Its weakness appears in connection with the uncontrolled inversion of the boot.

Patent No. 3938236 U.S. Pat. No. 3,187,848

An object of the present invention is an improved seal system with an optimized thermal design. A specific further object is an improvement in protection against ingress of foreign matter, for example fluids, which means to inhibit internal corrosion or fouling. Consequently, improved material protection against foreign intrusion while avoiding the drawbacks of the prior art is a primary object of the present invention. There is also a need for realized, rational, easy-to-install, worthwhile and cost-reliable design changes in terms of sealing systems, in which the risk of material ingress is specifically avoided in the event of a reversal movement. be.

In accordance with the present invention, all problems are addressed with a pressure relief valve means, which is normally closed and controlled and limited to an open state to relieve pressure when the pressure is not equal between the inside and the outside. , and an integrated pressure relief valve function that automatically and temporarily changes in a reversible manner. The present invention thus provides a pressure balance between the inside and the outside. Balancing avoids or limits boot deformation and consequent boot inversion. The present invention is associated with the exclusive benefit of effectively eliminating the falling off of the dust boot from the outer housing seat of the cylinder.

More specifically, the pressure relief valve mode is changed automatically and self-driven in a predetermined and controlled manner, without the supply of external energy, in particular current-free, but still in a predetermined and controlled manner, thereby making it surprisingly effective in continuous applications. Easy profit.

The pressure relief means of the seal system integrates the relief valve spring resilience, where the resilience of the relief valve integrated into the elastomeric flexible dust boot and its peripheral interface of the dust boot is defined by the relief valve body Integrating means whereby a part of the corresponding radially grooved seat of the housing and/or the actuating member/piston integrates the relief valve seat of the respective relief valve. More specifically, the pressure relief valve body in the interface section of the boot may be configured as a separate recess in the boot, the recess being connected to the inside but separated from the outside. As a result, the circumference of the boot may remain unchanged and all mechanical design changes may focus on modifying the elastomeric boot. Such design changes are relatively easy when the boot is made of rubber or other elastomeric material so that inexpensive replacement of the boot during maintenance allows the conventional cylinder (including its surroundings) to be replaced by the present invention. allows to effectively obtain all the advantages of

The boot tool is simplified if the boot comprises, in its interface section, a recess embodied as a longitudinal slot section arranged parallel to the linear displacement direction of the actuating member. Another alternative embodiment of the invention is that interface section that can be embodied as a longitudinal slot section that includes an anti- parallel slot design with walls that can be slanted or curved with respect to the central axis of the linear displacement direction. It may comprise a recess integrated therein. The latter effect is an extended slot length such that improved sealing against foreign material intrusion is achieved.

The resilience in valve function is easily changed by simply changing the thickness of the orthogonally arranged end walls/diaphragms. The end wall/diaphragm has a certain predetermined resilience, the resilience of the end wall corresponding to the required resilience of the relief valve means. As a result, the end walls can be designed with a reduced wall thickness compared to the average wall thickness of the boot.

If the interface portion integrates multiple recessed and/or slotted sections, the performance of the relief valve can be effectively improved. The same is true if the pressure relief valve means is integrated only in the first interface portion, or only in the second interface portion, or alternatively integrated in both interface portions. It also applies if Further adaptations are possible if the plurality of slot sections and/or interface portions are regularly arranged, particularly equidistantly and equiangularly with respect to each neighbor on the boot. It is further beneficial if the pressure relief valve means are integrated into all interface sections of the boot.

1 is an isometric cross-sectional view of a first embodiment of a hydraulic wheel cylinder with sealing means according to the invention, when the actuating member (piston) is fully retracted; FIG. FIG. 2 shows the same cylinder as in FIG. 1 with a compression spring spread between both actuating members. FIG. 3 is an exploded isometric view of the cylinder components. 4 is an exploded isometric view of the parts forming both actuating members of the cylinder of FIG. 1; FIG. Figure 5b is an enlarged cross-sectional detail view of the cylinder and boot detail marked V in Figure 5a for the first embodiment. Figure 6a is an enlarged front view and Figure 6b is an isometric view of a boot having slots integrated into its second radially inner interface region (first embodiment). Figure 7 is an enlarged cross-sectional view of the cylinder and boot detail marked V in Figure 2 for the second boot embodiment (slots integrated into the first radially outer interface region); Figure 8a is an enlarged front view of the boot embodiment in Figure 7 (second boot embodiment) with an integrated slot in its first interface region, and Figure 8b) is an isometric view is. FIG. 9 is a comparison of a cylinder embodiment in an isometric cross-section and its boot embodiment in an isometric view. FIG. 10 is a comparison of a cylinder embodiment in isometric cross-section and its boot embodiment in isometric view. Figures 11a, 11b are further variations (cross-sections) of the embodiment with anti-parallel (tilted) slots. Figures 12a, 12b are further variations (isometric views) of the embodiment with irregularly positioned slots.

Although various other applications in other brake system formations and applications are still possible, the present invention is one preferred embodiment for boot embodiments 1 and 2 as applicable in drum brake wheel cylinder formations. A more detailed description will be focused on, which will be explained in more detail in the following detailed description of the drawings.

The drum brake system according to the invention can be designed primarily in simplex, duplex, duo-servo or other constructive mechanical configurations. The drum brake system according to the invention generally operates in different functions according to very different functional modes, e.g. mode.

The drum brake system includes two opposed and mutually opposed circumferential friction surfaces of a rotatable brake drum in association with a rotatable vehicle wheel (not shown) that can frictionally cooperate in braking operation. Equipped with relatively expandable brake shoes. The wheel cylinders 3 are linear drives, e.g. expanders which may include hydraulic, mechanical and/or electromechanical subsystems, e.g. electric actuators with drive trains, e.g. , along with other suitable brake peripherals, such as drum brake linkage means. Each cylinder 3 comprises at least one or opposing displaceable actuating members 5,6 .

Cylinder 3 is generally rotationally fixed to a drum brake stator, which can be designed in a typical anchor plate shape, or alternatively designed as an axle component. In a preferred embodiment, the cylinder 3 can be designed as a hollow solid body knitted by mechanical interfaces with a mounting socket 16 and an integral internal thread 17 for external threaded mounting means such as a screw. In the case of an electric and/or hydraulic drive means configuration, each cylinder has an interface connector, for example an electric and/or hydraulic port means 18 which may be designed as an internal thread, a bleed valve means 19 at the vertical top of the hydraulic chamber 20, a hydraulic port 18 with a hydraulic chamber 20 in permanent hydraulic connection with a longitudinal cylinder bore 21 and also two opposing hydraulic working member pistons allocated for sealed relative axial displacement within the cylinder bore. Each actuating member piston carries its own sliding lip seal member 22,23. Finally, the compression spring member 24 is arranged such that both pistons generally flexibly expand away from each other to protect the nominal hydraulic chamber volume when the brake system remains idle in the brake release condition. , interposed axially between the two actuating member pistons. The ends of the compression spring member 24 can be assigned to opposite blind bores 25, 26 of both working member pistons.

The cylinder is elastically snapped and is thereby sealingly assigned to a position radially lowered from the radial outside into a radial groove of a seat 12 arranged on the outer surface of the expander housing 4, It comprises an annular flexible ring-shaped seal boot 1, 2 integrating at its first end a housing interface portion 9 comprising a radially inwardly directed flange 27 . The second ends of the ring-shaped seal boots 1,2 are elastically snapped so that they are radially outwardly inserted into grooves of seats 13 arranged on the outer surfaces of the actuating members (pistons) 5,6. It is constituted by a member interface portion 10 including a radially inwardly directed flange 28 sealingly assigned to a downwardly lowered position. As a result, both sheets 12, 13 and interface portions 9, 10 provide improved mechanical stability in addition to the flexible elastomeric sealing means/functions integrated into the respective flanges 27, 28 of boots 1, 2. Forms an overlapping, lowered serpentine shaped mechanical interaction seal system for spray water resistance. As a result, the described sealing system provides a generally hermetic (dust-tight, liquid-tight, gas-tight) sealing function between the inside (eg, "dry" room 11, 11') and the outside E.

The interface portions 9, 10 of the boot additionally comprise a normally closed pressure relief valve means and an implicit pressure relief valve function , which is separated between the boot 1, 2 and the housing 4. With respect to the rooms 11, 11' where the valve body is located, the valve body automatically and temporarily changes to an open state at a predetermined position under a pressure gradient drop in the direction from the inside to the outside E of the rooms 11, 11'. means that As a result, the sealing system permits a predetermined, controlled, and in this way limited, directed overpressure release, for example gas ejection from the rooms 11, 11' to the outside E. More specifically, the very specially designed sections of the boot flanges 27 , 28 allow the disc to be temporarily lifted above the opposing valve seat nut ground sections. , manages eruptions directed at integrating additional features and functionality. The process ends when the boot-integrated elastomeric check valve function ends in closing under equal pressure between the inside and outside E of the rooms 11, 11'. In other words, the "valve" flange portions of the boots 1,2 automatically return to their normal closed sealing position, sealed against the seats 12,13 in the nut ground section after ejection. All its functions are performed automatically by the elastomeric elasticity of the boots 1, 2 of the invention only under the influence of a pressure gradient. As a result, the invention operates spontaneously without external energy supply, in particular currentless. In a preferred embodiment, the pressure relief valve body (flange portion) of the boot integrates a separate recessed slot/channel shaped section 14, which recess 14 is typically connected to the inner room 11, 11' and which is also typically , is sealingly separated from the outside E by a flexible thin diaphragm/end wall 15 . The radially inner integral recesses 14 in the flanges 27, 28 may be embodied as longitudinal slot sections arranged parallel to the axial linear displacement direction of the actuating members 5, 6, each diaphragm , as a flexible end wall 15 arranged substantially perpendicular to the axial axis of displacement. Each end wall 15 has a specific predetermined resilience, the resilience of the diaphragm/end wall 15 corresponding to the required resilience for pressure differential control. The end wall/diaphragm 15 can in particular be designed with a reduced wall thickness compared to the average wall thickness dm of the boots 1,2. The interface portions 9, 10 of the boots 1, 2 may comprise multiple pressure relief valve sections, even if one interface portion 9, 10 integrates multiple recesses 14 and/or slot sections. means good . In this case, the plurality of valve body parts/slot sections 14 are preferably regularly arranged, they may be arranged in particular equidistantly and equiangularly to each other or to neighboring slots in the circumferential direction. . The valve function behavior can be affected by the total number of slots, the area/size of the slots and the elasticity of their diaphragms/end walls 15 .

11 and 12 focus on further valuable detailed variants of the boot 1 disclosed in the examples in relation to the first embodiment of the boot 1. FIG . More particularly, Figures 11a, 11b show a design variation of the anti-parallel slots 13 with a slot orientation that is tilted with respect to the central axis of displacement. FIGS . 12a, 12b disclose irregular application of the slanted slot 13 design variant. It is clear that all features disclosed in the examples, embodiments and variants can be combined in many ways also in connection with the boot 2 embodiment.

Various further modifications, alternatives and embodiments of the disclosed features are still possible. As a result, the pressure relief valve means may be integrated only within the second interface portion 10 of the boot 1 (as shown in FIGS. 1-5) or the relief valve means may be integrated into the first interface portion 10 of the boot 2 (as shown in FIGS . 7 and 8). In an alternative embodiment, all interface portions 9, 10 of the boot may be provided with pressure relief valve means so that uncontrolled displacement (inversion) of the dust boot is most effectively avoided.

1,2 boot 3 cylinder 4 housing 5,6 actuating member 7 cylinder bore 8 bellows 9,10 interface portion 11,11' room 12,13 seat 14 recess/slot 15 end wall 16 mounting socket 17 internal thread 18 hydraulic port 19 bleed means 20 hydraulic chamber 21 longitudinal cylinder bore 22, 23 lip seal 24 compression spring 25, 26 blind bore 27, 28 flange E outer Ax axial R radial dm average thickness

Claims (17)

A flexible dust boot (1, 2) for a motor vehicle brake cylinder (3), comprising:
The cylinder (3) is
a housing (4);
drive means for linear actuation of actuating members (5, 6) arranged in cylinder bores (7) of said housing (4); and
the actuating members (5, 6) are movably guided relative to said housing (4);
Said boots (1, 2) are provided with two concentric rings with different diameters for flexible sealing protection of inner rooms (11 , 11' ) separated from the outside surrounded by said boots (1, 2). A flexible bellows (8) is provided between the interface portions (9, 10) so that said boots (1, 2) are sealed between the actuating members (5, 6) and the housing (4). providing blocked relative displacement and protecting against foreign material intrusion from outside to inside of said housing (4), said both interface parts (9, 10) connecting housing (4) and actuating member In the flexible dust boots (1, 2) resting radially outward on their respective corresponding sheets (12, 13) in the upper grooves (5, 6),
each of the two interface portions (9, 10) opposite the seats (12, 13) comprises a flange (27, 28) acting as pressure relief valve means ;
Flexible, characterized in that said flanges (27, 28) automatically and temporarily change to an open state under a pressure gradient drop in said outward direction from the inner chamber (11, 11') . sex dust boots (1, 2). 2. According to claim 1, characterized in that said flanges (27, 28) are normally closed when the pressure between the inner chamber (11, 11') and said outer side is equal or balanced. A flexible dust boot (1, 2) for a motor vehicle brake cylinder (3) as described. 3. Motor vehicle brake cylinder according to claim 1 or 2, characterized in that said flanges (27, 28) are automatically self-actuated and controlled under pressure differentials and without supply of external energy. Flexible dust boots (1,2) for 3). Motor vehicle brake cylinder (3) according to any one of claims 1 to 3, characterized in that said actuating members (5, 6) each comprise a sealing member (22, 23) against the cylinder (3). ) for flexible dust boots (1, 2). the elasticity of the relief valves of said flanges (27, 28) being integrated into said flexible boots (1, 2);
said interface portions (9 , 10) are integral with flanges (27 , 28);
5. The method of claims 1 to 4, characterized in that the relief valve seats of the flanges (27, 28) are integrated into the parts of the corresponding radially grooved seats (12, 13). A flexible dust boot (1, 2) for a motor vehicle brake cylinder (3) according to any one of the preceding claims. Flanges (27, 28) in said interface portions (9, 10) are integrated with recesses (14), said recesses (14) being connected to inner rooms (11, 11') . A flexible dust boot for a motor vehicle brake cylinder (3) according to any one of claims 1 to 5, characterized in that it is separate from the outside of the boot (1, 2). (1,2). Said recesses (14) in said interface portions (9, 10) are embodied as slots arranged obliquely or parallel to the linear displacement direction of said actuating members (5, 6). A flexible dust boot (1, 2) for a motor vehicle brake cylinder (3) according to claim 6 , characterized in that CHARACTERIZED IN THAT said recesses (14) in said interface portions (9, 10) are embodied as slots arranged parallel to the linear displacement direction of said actuating members (5, 6). A flexible dust boot (1, 2) for a motor vehicle brake cylinder (3) according to claim 6, wherein: Said recess (14 ) is separated from said outer side by an end wall (15) which is perpendicular to the direction of linear displacement of said actuating members (5, 6). A flexible dust boot (1, 2) for a motor vehicle brake cylinder (3) according to any one of claims 6 to 8, characterized in that it is arranged as a. Said end wall (15) is provided with a predetermined resilience and said resilience of said end wall (15) is the resilience required for the pressure gradient that actuates the flanges (27, 28) . A flexible dust boot (1, 2) for a motor vehicle brake cylinder (3) according to claim 9, characterized in that For a motor vehicle brake cylinder (3) according to claim 9 or 10, characterized in that said end wall (15) has a wall thickness less than the mean wall thickness of said boots (1, 2). Flexible dust boots (1,2). Motor vehicle brake cylinder (3) according to any one of claims 6 to 11, characterized in that said interface portions (9, 10) are integrated with a plurality of recesses (14). Flexible dust boots (1, 2) for. The plurality of recesses (14) are regularly arranged in the circumferential direction of the cylinder (3) at equal intervals or at equal angles to adjacent recesses (14). 13. A flexible dust boot (1, 2) for a motor vehicle brake cylinder (3) according to 12. said interface portions (9, 10) comprising a first interface portion (9) and a second interface portion (10);
The flanges (27, 28) are
14. According to any one of claims 1 to 13, characterized in that it is integrated in at least one of the first interface part (9) or the second interface part (10) . A flexible dust boot (1, 2) for a motor vehicle brake cylinder (3). 15. Motor vehicle according to any one of claims 1 to 14, characterized in that said flanges (27, 28) are at least partially integrated in the interface parts (9, 10). Flexible dust boots (1,2) for brake cylinders (3). said interface portion (9, 10) comprises a first interface portion (9) and a second interface portion (10);
Said seats (12, 13) comprise a first seat (12) having a first outwardly-opening radial groove in the outer surface of said housing (4) and on the outer surface of said actuating members (5, 6) a second seat (13) having an outwardly-opening radial second groove positioned in the
the first interface portion (9) is resiliently snapped into said first groove ;
16. Motor vehicle brake cylinder (1) according to any one of the preceding claims, characterized in that the second interface part (10) is elastically snapped into said second groove . Flexible dust boots (1,2) for 3). Flexible dust boot for a motor vehicle brake cylinder (3) according to any one of claims 1 to 16, characterized in that said flanges (27, 28) are normally sealed. 1, 2).

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